18" Square Setup - What size Tyres....?

Alloy wheels and tyre discussion
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Darkangelv2
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18" Square Setup - What size Tyres....?

Post by Darkangelv2 » Tue May 22, 2018 3:42 pm

Hi All

I've found some nice 18" wheels that are 8.5J & ET37 all round. They would need new tyres so i would assume i would compensate for the lack of stagger by adding a little 'meat' to the rear?

Does anyone have experience of running a square setup with 18's (on a non-M) and what tyre combo have you run? Do i need spacers too?

PS. I'm running BCR Coilovers so can adjust height as required.

Thanks :thumbsup:
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patriot66
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18" Square Setup - What size Tyres....?

Post by patriot66 » Tue May 22, 2018 10:05 pm

I'm fairly certain the front et 37s will rub on the wheel arch liner where the bumper/wing join is. I am running a set of 18" staggered 8j/8.5j MV3s which are et 34 front and et 37 rear with 225/40 front and 255/35 rear. My front et 34s used to rub on high speed compression bumps until I recently fitted new Bilstein B4s. Your et 37s on the front will put the tyre shoulder further out by 3mm and right under the metal edge of the wing :( You will be fine with et 37/8.5j on the rear and you won't need spacers as the tyres are more or less flush with the wing if you use 255/40 :thumbsup:
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18" Square Setup - What size Tyres....?

Post by Mr Tidy » Tue May 22, 2018 11:49 pm

I've not done it yet, but I have a set of 224s that are square 8J x 18" ET 42 (so I actually have 4 fronts)!

Someone suggested running 225/40 X 18 on the front and 245/40 X 18 on the rears, but I need to have a trial fitting.

Anyway I hope this may help:- https://www.willtheyfit.com/
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18" Square Setup - What size Tyres....?

Post by rally-chris » Wed May 23, 2018 12:59 am

I’m running standard staggered Z4 tyre sizes on 8.5” x 18” ET35 rims so you should be fine to do the same as your wheels will be 2 mm further in.
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18" Square Setup - What size Tyres....?

Post by Darkangelv2 » Wed May 23, 2018 3:24 pm

So, in the main, you guys are keeping the tyre size the same as a staggered setup rather than compensating for the (small) rim width difference.

I agree with what you've mentioned patriot66 but think i can counter it with some creative geometry :wink:

So, i'm thinking i'd go with

Front - 225 - 40 - R18 (Standard tyre so will be slightly more stretched on)
Rear - 255 - 40 - R18 (M size tyre for a bit more meat)
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18" Square Setup - What size Tyres....?

Post by philbo909 » Wed May 23, 2018 5:20 pm

Darkangelv2 wrote:
Wed May 23, 2018 3:24 pm
So, in the main, you guys are keeping the tyre size the same as a staggered setup rather than compensating for the (small) rim width difference.

I agree with what you've mentioned patriot66 but think i can counter it with some creative geometry :wink:

So, i'm thinking i'd go with

Front - 225 - 40 - R18 (Standard tyre so will be slightly more stretched on)
Rear - 255 - 40 - R18 (M size tyre for a bit more meat)
Try 245/40/18 on the rear, cheaper and a little more sidewall. Perfect size for 8.5J
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18" Square Setup - What size Tyres....?

Post by Darkangelv2 » Wed May 23, 2018 7:04 pm

philbo909 wrote:
Wed May 23, 2018 5:20 pm
Darkangelv2 wrote:
Wed May 23, 2018 3:24 pm
So, in the main, you guys are keeping the tyre size the same as a staggered setup rather than compensating for the (small) rim width difference.

I agree with what you've mentioned patriot66 but think i can counter it with some creative geometry :wink:

So, i'm thinking i'd go with

Front - 225 - 40 - R18 (Standard tyre so will be slightly more stretched on)
Rear - 255 - 40 - R18 (M size tyre for a bit more meat)
Try 245/40/18 on the rear, cheaper and a little more sidewall. Perfect size for 8.5J
Cool, I’ll take a look. I did notice the number of brands restrict when I put in the new size.
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18" Square Setup - What size Tyres....?

Post by ben g » Thu May 24, 2018 9:50 am

patriot66 wrote:
Tue May 22, 2018 10:05 pm
I'm fairly certain the front et 37s will rub on the wheel arch liner where the bumper/wing join is. I am running a set of 18" staggered 8j/8.5j MV3s which are et 34 front and et 37 rear with 225/40 front and 255/35 rear. My front et 34s used to rub on high speed compression bumps until I recently fitted new Bilstein B4s. Your et 37s on the front will put the tyre shoulder further out by 3mm and right under the metal edge of the wing :( You will be fine with et 37/8.5j on the rear and you won't need spacers as the tyres are more or less flush with the wing if you use 255/40 :thumbsup:
You've got your offset figures the wrong way around. ET37 means the wheel will sit further in the wheel arch than ET34.

Unsure why so many people get this wrong. It's pretty basic stuff.
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18" Square Setup - What size Tyres....?

Post by Darkangelv2 » Thu May 24, 2018 10:10 am

ben g wrote:
Thu May 24, 2018 9:50 am
patriot66 wrote:
Tue May 22, 2018 10:05 pm
I'm fairly certain the front et 37s will rub on the wheel arch liner where the bumper/wing join is. I am running a set of 18" staggered 8j/8.5j MV3s which are et 34 front and et 37 rear with 225/40 front and 255/35 rear. My front et 34s used to rub on high speed compression bumps until I recently fitted new Bilstein B4s. Your et 37s on the front will put the tyre shoulder further out by 3mm and right under the metal edge of the wing :( You will be fine with et 37/8.5j on the rear and you won't need spacers as the tyres are more or less flush with the wing if you use 255/40 :thumbsup:
You've got your offset figures the wrong way around. ET37 means the wheel will sit further in the wheel arch than ET34.

Unsure why so many people get this wrong. It's pretty basic stuff.
I thought exactly the same Ben - but when you factor in the extra half inch in wheel width it IS 3MM nearer the outer arch :thumbsup:

PS. I didn't know whether it was luck or judgement ! :rofl:
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18" Square Setup - What size Tyres....?

Post by ben g » Thu May 24, 2018 10:18 am

Darkangelv2 wrote:
Thu May 24, 2018 10:10 am
ben g wrote:
Thu May 24, 2018 9:50 am
patriot66 wrote:
Tue May 22, 2018 10:05 pm
I'm fairly certain the front et 37s will rub on the wheel arch liner where the bumper/wing join is. I am running a set of 18" staggered 8j/8.5j MV3s which are et 34 front and et 37 rear with 225/40 front and 255/35 rear. My front et 34s used to rub on high speed compression bumps until I recently fitted new Bilstein B4s. Your et 37s on the front will put the tyre shoulder further out by 3mm and right under the metal edge of the wing :( You will be fine with et 37/8.5j on the rear and you won't need spacers as the tyres are more or less flush with the wing if you use 255/40 :thumbsup:
You've got your offset figures the wrong way around. ET37 means the wheel will sit further in the wheel arch than ET34.

Unsure why so many people get this wrong. It's pretty basic stuff.
I thought exactly the same Ben - but when you factor in the extra half inch in wheel width it IS 3MM nearer the outer arch :thumbsup:

PS. I didn't know whether it was luck or judgement ! :rofl:
Ok, now I look like a moron :lol: I assumed the square set up was 8J front and rear. I must put my glasses on before browsing the Internet! Apologies to patriot :thumbsup:

I read it about 3 times to make sure I wasn't reading it wrong aswell!!!

For what it's worth, I had 19x8.5J et 35 on the front of my Z4 a while back. The 235/35/19 tyres used to rub in the usual area, but when I switched to 225/35/19, it was fine, so you should be OK, providing your suspension isn't buggered. I was lowered on eibach springs, so I think if you're on sport sprints, it shouldn't be an issue.

After I swapped mine out for new Bilstein B4's, the front raised about 5mm or so, which gave me a little more clearance.
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18" Square Setup - What size Tyres....?

Post by patriot66 » Thu May 24, 2018 8:45 pm

Apologies fellas :D I do understand about wheel offset (honest !) I just didn't explain myself very well :oops: I must lay off the red wine :rofl:
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